This invention relates generally to pump dispenser having a reduced number of parts, the dispenser having its plunger containing a discharge spout locked in a up position to avoid leakage during intervals of shipping and storage and to function as a childproof and safety feature.
Many pump dispensers are known as having lock-up and/or lock-down plunger features of various styles and structures. Many of such locking plunger dispensers provide for relative rotation between longitudinally extending ribs and grooves into misalignment and alignment of inoperative and operative positions of the plunger. However, many of such known dispensers require separate, rotatable lock collars to effect a match and mismatch between the ribs and grooves, thereby requiring at least one additional molded part which adds to the cost of the dispenser.
U.S. Pat. No. 4,162,746, commonly owned herewith, discloses a dispenser having a lock-up plunger requiring a rotatable lock ring in the form of an annular sleeve for matching and mismatching ribs on the piston stem with grooves at an inner wall of the lock ring.
U.S. Pat. No. 3,489,322 discloses another type plunger lock-up dispenser eliminating the need for a lock ring and instead providing for a match and mismatch between ribs and grooves upon relative rotation of the plunger head. However, the discharge spout is not made part of the head but is rather formed on a separate part which snap-fits together with the container closure, thereby significantly adding to the cost of the package.
Besides, these and other known plunger lock-up dispensers are not positively retained in the locked position such that the plunger head can be unintentionally rendered operative upon only a slight backoff from the misaligned position. Thus, if a dispensing package is dropped or nudged liquid product could easily leak from the spout even after the user has locked the plunger in place. Also, without a positive lock, a child of tender years can quickly figure out a way to unlock the plunger head thereby either creating a mess or an unsafe condition.
Many pump dispensers are of the type having a lost motion between the piston and piston stem, the latter being hollow and having lateral discharge ports which are uncovered upon a relative shifting movement of the stem upon plunger actuation. Typically, a container vent passage is closed in the at-rest condition of the plunger by an upper seal of the piston cup which operates within the pump cylinder. It is undesirable for the piston cup to be used in such manner for the opening and closing of the container vent passage as the seal could deteriorate thereby causing leakage.